The invention more particularly concerns a device for controlling the temperature of a battery onboard a motor vehicle, the temperature control device including:
an air-conditioning circuit of the motor vehicle in which circulates a first heat-transfer fluid termed the “air-conditioning fluid”, the air-conditioning circuit including at least one evaporator for direct transfer of heat emitted by the battery to the air-conditioning fluid, a compressor making it possible to increase the pressure and the temperature of the air-conditioning fluid;
a cooling circuit in which circulates a second heat-transfer fluid termed the “cooling fluid”, the cooling circuit including at least one first heat source adapted to heat the cooling fluid and at least one main radiator for cooling the cooling fluid that can be short-circuited.
An electric or hybrid motor vehicle is driven at least in part by a traction electric motor that is supplied with electricity by a traction battery. The performance of the traction battery can vary greatly as a function of its temperature.
If the battery is subjected to very low temperatures, for example temperatures below zero, it loses its energy capacity. Fast charging of the battery may then be prohibited. It is therefore necessary to heat the battery before charging it.
Similarly, using the battery produces heat. If the battery is already overheated, either because of a high ambient temperature or because of too rapid alternation of discharging and charging, it can be necessary to prohibit the use of the battery to protect the cells. This generally involves immobilizing the vehicle for the time taken for the battery to cool to an acceptable operating temperature.
To solve these problems, it is known to equip the vehicle with a device for controlling the temperature of the battery in order to maintain the cells of the battery within a range of optimum operating temperatures.
Thus it has been proposed to equip the battery with a heat-transfer fluid circuit that makes it possible to cool it or to heat it, as required.
Thus, in the application DE-A1-10 2007 004 979, the heat-transfer fluid circulates in an air-conditioning circuit of the vehicle. In this way, the battery is cooled in parallel with the passenger compartment of the vehicle.
Moreover, the electrical control of the battery is handled by an electronic control unit that gives off a great deal of heat when operating. To prevent damage to the electronic components of this unit, it is cooled by a cooling circuit separate from the air-conditioning circuit. A main radiator makes it possible to dissipate the heat emitted by the electronic control unit.
To make it possible to heat the battery, it is known to use the heat given off by the electronic control unit. To this end, a heat exchanger makes it possible to transfer heat conveyed by the cooling fluid to the air-conditioning fluid circulating in the air-conditioning circuit.
To improve the capacity for heating the battery, the cooling circuit is equipped with a pipe that is able to short-circuit the main radiator when the battery needs to be heated.
A device of the above kind as described in DE-A1-10 2007 004 979 nevertheless has numerous disadvantages. Thus the adaptation of the heat exchanger to make it possible to heat the air-conditioning fluid before being able to heat the battery leads to an additional cost in the manufacture of the temperature control device.
Moreover, the heat given off by the electronic control unit is not entirely transmitted to the battery because some heat is lost in the heat exchanger. This device is therefore not totally effective.
Moreover, the prior art device does not make it possible to heat the battery rapidly when starting the vehicle from cold. In fact, the electronic control unit begins to heat up only after a certain time of use. During this time lapse, no source of heat is available for heating the battery. It is therefore necessary to use thermo plungers, which consume a very large amount of energy.